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create table tb(tid varchar(6),rq datetime,rk int,cl int)

Insert into tb
Select 1,'2009-8-11',100,20 union all
Select 1,'2009-10-11',0,50 union all
Select 1,'2009-11-11',10,60


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  rq    tid  ÆÚ³õÊýÁ¿ rl  cl  ÆÚÄ©ÊýÁ¿
200908    1      0    100  20    80
200909    1      80    0    0    80
200910    1      80    0    50    30
200911    1      30    10  60    -20
.................

rl¾ÍÊǽøµÄÊýÁ¿£¬cl¾ÍÊdzöµÄÊýÁ¿£¬200908µÄÆÚ³õÊýÁ¿Îª0ÊÇÒòΪ´Ó8Ô¿ªÊ¼

---

SQL code:
---²âÊÔÊý¾Ý---
if object_id('[tb]') is not null drop table [tb]
go
create table tb(tid varchar(6),rq datetime,rk int,cl int)
go
Insert into tb
Select 1,'2009-8-11',100,20 union all
Select 1,'2009-10-11',0,50 union all
Select 1,'2009-11-11',10,60
go

---²éѯ---
select
convert(varchar(8),rq,112) as rq,
tid,
ÆÚ³õÊýÁ¿=isnull((select sum(rk-cl) from tb where tid=t.tid and rq<t.rq),0),
rk,
cl,
ÆÚÄ©ÊýÁ¿=isnull((select sum(rk-cl) from tb where tid=t.tid and rq<t.rq)